The present invention relates to a gas injection apparatus and method for injecting a gas into a flowing liquid with the objective of dissolving the gas into the liquid.
There are many prior art systems and devices that require the injection of a gas into a liquid, for instance, low viscosity fermentation systems, waste-water treatment systems, etc. By way of an example, in prior art waste-water treatment plants, airborne oxygen is dissolved in an atomized spray of waste water produced by a sprinkler system. Such oxygen addition, referred to in the art as aeration, destroys water-borne bacteria and reduces hydrocarbon contaminants.
Since air only contains about 21% oxygen, a more recent development in waste-water treatment is to inject pure oxygen directly into the waste water. At normal ambient temperatures, however, the dissolution rate of oxygen in water is rather slow; and thus, the prior art has provided injection devices and methods to enhance the oxygen dissolution rate in water. For example, in U.S. Pat. No. 3,928,199, oxygen is injected into a stream of flowing waste water which upon reaching a fall section, undergoes a precipitous drop to a lower level at which the falling water generates a highly turbulent zone. The turbulent zone of falling water produces a high rate of oxygen transfer into the waste water. As may be appreciated, U.S. Pat. No. 3,928,199 requires construction of a series of rises and drops for the falling water.
U.S. Pat. No. 4,834,343 discloses a device that is more compact than the arrangement set forth in the aforementioned '199 patent for injecting a gas into a liquid, such as oxygen in water. In U.S. Pat. No. 4,834,343, the dissolution of the gas into the liquid occurs in a vertical column. Liquid enters at the top of the column in two streams, one vertical and the other horizontal. The vertical stream produces a vertical downflow within the column. The gas is bubbled into the horizontal stream which also acts to impart rotational movement to the downflow. The gas bubbles are moved in a cyclonic motion and dissolve within the liquid before discharge at the bottom of the column. As may be appreciated a branching arrangement of pipes, fittings etc. and a specially fabricated column are incorporated in the device disclosed in the '343 patent.
As will be discussed, the present invention provides an apparatus and method for injecting a gas into a liquid that is more compact and less complicated than the apparatus and methods of the prior art.